Various sensors to detect characteristics of a material to be irradiated by irradiating light from a light-emitting element to the material to be irradiated and receiving the regularly reflected light and diffuse-reflected light with respect to the light incident on the material to be irradiated by a light-receiving element have been proposed previously. These sensors have been utilized in broad fields and have been used for the wide variety of applications, for example, photointerrupters, photocouplers, remote control units, IrDA (Infrared Data Association) communications devices, optical fiber communications devices and, furthermore, manuscript size sensors.
In such a sensor, for example, in the case where the regularly reflected light of the light irradiated from a light-emitting element to a material to be irradiated is received by a light-receiving element, it is preferable that the light-emitting element and the light-receiving element be disposed at locations closer to each other in order to receive the regularly reflected light by the light-receiving element more accurately.
For example, Japanese Unexamined Patent Application Publication No. 8-46236 describes a light-receiving and emitting element array in which one surface of a silicon semiconductor substrate is doped with an impurity and a shallow pn junction region taking responsibility for a light-receiving function and a deep pn junction region taking responsibility for a light-emitting function are disposed adjoining to each other.
However, in the case where a light-receiving element and a light-emitting element are integrally disposed on the same substrate, when the light-emitting element is driven, a leakage current (so-called noise current) is generated and may flow into the light-receiving element through the silicon substrate. This leakage current admixes as an error component (noise) with the output current (current output in accordance with the intensity of the received light) from the light-receiving element. Consequently, the light-receiving and emitting element in the related art has an issue that the accuracy in detection of the reflected light by the light-receiving element is reduced because of generation of such a noise current. This leakage current increases as the light-receiving element and the light-emitting element are disposed at locations closer to each other. That is, it is desirable that a light-emitting portion be closer to a light-receiving portion in order to receive the regularly reflected light by the light-receiving element accurately, but on the other hand, a leakage current relatively increases. Therefore, there is an issue that the detection accuracy of the light-receiving and emitting element array in the related art cannot be relatively improved.
The present invention has been made in consideration of the above-described problems and an object is to provide a light-receiving and emitting device exhibiting relatively high accuracy in detection of the reflected light by a light-receiving element, wherein a leakage current generated by driving of a light-emitting element is relatively suppressed from flowing into the light-receiving element even in a light-receiving and emitting device including an integrated light-receiving and emitting element in which a light-receiving element and a light-emitting element are integrally disposed close to each other on the same substrate.